Drill geometry for soft alloys: For drilling aluminium and other soft, ductile materials, the recommended drill helix angle is typically greater than 30°. Evaluate the statement.

Introduction / Context:
Drill helix (rake) angle influences chip evacuation and cutting action. Soft, ductile materials like aluminium produce continuous, long chips that require efficient lifting and removal from the hole to avoid packing and surface damage. Tool geometry is adjusted accordingly.

Given Data / Assumptions:

• General-purpose twist drills for aluminium and similar soft metals.
• Adequate lubrication or mist is available to reduce built-up edge.
• HSS or carbide drills used under normal shop conditions.

Concept / Approach:
Higher helix angles (often 35°–45°) provide a more aggressive rake and larger flute volume, enhancing chip lifting and evacuation. This reduces the tendency of chips to jam, lowers cutting forces, and improves hole finish. In contrast, low helix angles are favored for hard or abrasive materials to strengthen the cutting edge and moderate chip flow.

Step-by-Step Solution:

Verification / Alternative check:
Tool catalogs list “aluminium geometry” drills with 35°–45° helix, polished flutes, and sharper point/rake to resist built-up edge and improve chip flow.

Why Other Options Are Wrong:

• Disagree/low helix recommendations contradict widely accepted practice for ductile chip forms.
• Limiting correctness to specific alloys or carbide tools is unnecessary; the principle holds for both HSS and carbide across most aluminium grades.

Common Pitfalls:
Using standard 30° helix without polished flutes may still work but can increase chip packing in deep holes. Peck drilling and proper coolant further improve results with high helix designs.

Final Answer:
Agree